1. Field of the Invention
This invention relates to positive displacement apparatus of the general type used as superchargers on internal combustion engines and in other applications. More particularly it relates to such apparatus in which two or more compression chambers are capable of lateral movement to accommodate circular motion of the pistons and in which the driving forces for the chambers are derived from forces originating independently from the forces generated by movement of the pistons.
2. Description of Related Art
Various attempts have been made to provide compressors in which the chamber and piston assemblies are arranged to permit lateral movement during the cyclic operation of the pistons. Skarlund U.S. Pat. No. 2,130,037 describes a compressor having an outer housing with flat parallel inner sides which contains a box-shaped outer piston that itself forms a housing for a second box-shaped inner piston reciprocating at an angle of ninety degrees to the direction of movement of the first piston. U.S. patent application Ser. No. 07/305,810 filed Feb. 3, 1989 (now U.S. Pat. No. 5,004,404), which application is assigned to the same assignee as the present application, describes a compressor in which oppositely disposed pistons follow a circular path while the respective chambers housing the pistons follow lateral reciprocating paths.
In these and other similar devices, the chambers are driven laterally by the forces applied to the chamber walls by the piston rings carried by the pistons. The force of the lateral component of movement of the piston applies the driving force to the chamber. Unless the forces generated by opposing pistons are precisely balanced, a twisting or rotational torque is produced on the chamber assembly increasing friction and wear. In actual practice, relatively large uncompensated rotational torques are produced because of mechanical tolerances and other factors. This rotational torque is resisted by a linear rotary bearing or other arrangement that is positioned adjacent the eccentric drive for the pistons.
William Milburn, Jr. U.S. Pat. No. 4,466,335 describes a co-piston type device where the functions of sealing and chamber drive ar separated and replaced by sealing strips and rolling element drive systems. The described arrangement fails to address the problem of rotational torque. Perhaps, more importantly, the inner piston remains as the principle means of transmitting transitional force to the outer piston/chamber assembly.